The present invention relates to a method and apparatus for controlling the mixing of two fluids of the same state (e.g. two gases, or two liquids) or of substantially the same state (e.g. a gas and fine liquid droplets). The invention is particularly useful in applications wherein it is desirable to enhance or otherwise control the mixing of the two fluids for promoting combustion or other chemical reactions, suppressing audible jet noise, or increasing the output of ejector pumps. The invention is therefore described below particularly with respect to such applications, but it will be appreciated that the invention could also be advantageously used in many other applications involving the control of mixing of two fluids.
The design criteria in many mixing processes are presently established on the basis of available data in a turbulent mixing layer. It is generally believed that the mixing process cannot be affected appreciably without a significant loss of energy. In particular, it is not considered possible to control the rate of mixing by altering only slightly the initial condition of the flow at its origin. Statements implying that the turbulent shear layers quickly become self-similar, thus losing the effect of their initial conditions, are still quite often made in the professional literature.
The foregoing concept directly affects the determination of the length of a combustion chamber or other mixing chamber, the determination then depending on the quantity of fluids which are to be mixed, their rate of reaction, the pressure gradients, and the velocities of the individual streams. A large body of experimental data provides empirical or semiempirical relations which are used in the design of combustors, flame holders, after-burners in turbo-jet engines, ram jet engines, gas-dynamic lasers, and even air curtains. In many cases, the combustors or mixing chambers could be made of shorter length if the mixing process could be enhanced, thereby conserving costly materials and weight in the manufacture of the engines, augmentors, and the like. Control or partial control (not necessarily enhancing) of the mixing process could produce advantages in many other applications, e.g., suppressing audible jet noise, inhibiting mixing in air curtains, and the like.